Electrical conductor and mounting same in electrical apparatus.



R. RUDENBERG.

ELECTHICAL CONDUCTOR AND MOUNTING SAME IN ELECTRICAL APPARATU&

APPLICATION FLED SEPT. 18. 1913.

Patented Nov. 19, 1918.

/l/l//ll/ channels in the active iron of the stator.

UNITED STATES EATENT osman BEINHOLD R''DENBERG, OF BERLIN-'WESTENIL GERMAN, ASSIGNOB TO SIEMENS- SCHUCKERTWERKE, Gr. M. B. H OF BERLIN, GERMANY, A CORPORATION OF GERMANY.

ELECTRICAL CONDUCTOR. AND MOUNTING SAME IN ELECTRIGAL APPARATUS.

Patented N (W. 19 1918.,

Application filed September 18, 1913. Serial No. ?90,533.

To all whom ?It may conccm:

Be it known that I, REINHOLD Rnmaenns, a German citizen, and resident of Berlin- `Westend, Germany, have invented certain new and useful Improvements in Electrical Conductors and Mounting Same in Electrical Apparatus, of which the following is a full, clear, and concise specification.

My invention relates to means for cooling electrical machinery and' more especially to high voltage dynamos. The object of my invention is to provide improved means for cooling the stator of a machine of this character;

As is well known to those skilled in the art, the heat generated in the stator conductors of a high voltage dynamo cannot escape at the circumference of the conductors, for the reason that they are embedded in a thick-walled tube of nsulating material, contained in the Slots of said stator. In the past, it has been customary to prevent the temperature in the interior of the active stator iron from becoming excessive and thus spoiling the electrical etficiency of the machine, by cooling the end connections of the conductors and providing coolirg the modern highly utilized dynamos this method of cooling has been found to be inadequate, the' electrical efl'ect of machinery of this class' having been, in fact, greatly impaired by reason of the impossibility of quickly eliminating the heat which accumulates in the stator.

My invention contemplates suitable and eflicient means for disposing of the heat generated in the conductors of the stator of a high voltage dynamo by employing hollow conductors instead of solid ones, the radiation surface of such hollow conductors being far greater than the surface of solid conductors. 'More'over by passing an air current through these hollow conductors a very eflicient abduction of heat from the interior of the conductors can be easily obtained and this abduction of heat may be rendered still more eflicientin machines of greater axial length by providing openings in the middle part of the conductors and of the insulating tubes surroundingthem, corresponding openings being provided in the stator body se that a constant current of air can be made to enter the open ends of the hollow conductors and after passing through theni to escape by way of the openngs n the middle part of the conductors and insulating tubes and through the radial openlngs provided in the stator. The heatladen air finally escapes through openings in the casing of the stato'.

My invention will be more fully .understood by reference to the accompanying drawing of which Figures l and 2 are crosssectons of forms of conductors according to my present invention, Fig. 3 is a vertical longtudinal section of a high voltage dynamo whose stator is provided With such conductors and with means for creating a current of air from both sides of the machine through the conductors and through the central part of the stator. In my copending application Serial No. 126320, filed October 18th, 1916, which application is a division of the present case, I have described and claimed certain modifications of the apparatus hereinafter described and claimed.,

I ani aware that it is old to employ hollow conductors or conductors provided with longitudinal channels extending all through their length in connection With the rotating parts of electric machinery, the hollow conductors being used in these cases also for cooling the conductors and the rotating parts carrying them. The problem of cooling rotating parts such as for instance, the rotor of a dynamo by providing longitudinal channels in the conductors, arranged on the periphery of such a rotor, was easy to solve on account of the centrifugal action exerted upon the air contained in these channels during rotation of the tubes around the dynamo shaft at high speed.

In contradistinction to this, there are a number of reasons which seem to make it undesirable to make the conductors of the stators of a high voltage dynamo hollow. As is well known, the size of modern high voltage dynamos is limited by the permissihle circumferential velocity of the rotor..

depends mainly upon the sectional area of the conductors and the eiiciency depends upon the resistance offered by these con- (MctOrS. Therefore the idea of abducting the heat generated within the conductors by making them hollow and passing a current of air through them, does not seem to be consistent with the condition that the resistance of the conductors should be kept as low as possible; for by making them hollow, the' resistance of the conductors is greatly increased. On the other hand, it seems impossible to employ hollow conductors havng a greater cross-section for the reason that then the cross-section of the slots would have to be increased also. This, however, is impossible, owing to lack of space and to the greater saturation obtained by reducing the thickness of the slot walls, such increase of saturation resulting in increased losses of electrical energy. On the other hand, the skin eftect brings it about that substantially no current flows through the central part of the conductors, most of the current being caused to flow near the inner periphery ot' the stator. This skin effect would exist in alternating current dynamos as well as n direct current dynamos, whose armature coils carry current of fiuctuatirig or alternating electro-motive force, which current may be of considerable frequency the high speed at which these machines must necessarily be operated.

' Now, practical tests have shown that contrary to what would have been expected for the reasons eXplained, the advantages gained by using hollow conductors in the stator of a high voltage dynamo, by far eX- ceed the disadvantagcs connected with this arrangement, so that the efl'ect of a high voltage dynamo provided with a cooling arrangement of thekind described above, is improved by about 30 per cent.

Referring first in a more general way to the drawing, similar denominations indicate similar parts throughout the figures, The insulating material is designated by the letter z', the channel which according to my invention is provided longtudinally in the conductor is designated by c, and the solid conductive material of the conductor is designated by s.

Referring now more particularly to the drawing in Fig. l I have shown a solid conductor having a channel which for instance may be made of rectangular cross-section. This conductor may be made by drawing over a mandrel, or by rolling a rectangular tube such as shown in Fig. 2. The cunductor shown in Fig. 2 diifers from the one described above only in the cross-sectional area of the channel whichis much greater in this case than in the former.

In Fig. 3, a) is the stator of a high voitage dynarno, and c, c are conductors such as shown in Figs. 1 and 2, inserted in slots w, u'. extending across the inner periphery of said stator. m is the stator casing and a and b are pressure chambers arrangcd on both' sides of said casing. d and e are intakes leading from below into said pressure chambers and 0, 0 are openings arranged in the middle part of the conductors c and insulating tubes z', i surrounding them, while 7 7* are r adial openings extending through the active iron of the stator and connecting the interior of the conductors with the exhaust chamber p in the central part of the casing. g is an exhaust outlet at the bottom of the casing. .2, z are fans or ventilators arranged at both ends of the rotor y.

When the machine is running, the ventilators e will draw in air from outside through the intakes (Z and c and this air is then pressed into the pressure chambers a, and b and from there through the end openings of the hollow conductors c toward the center of the machine in order to escape through the central openings 0 and r into the central chamber p and exhaust g. In this manner a very eflicient cooling action s obtained, the heat generated within the conductors as well as part of the heat generated in the active iron z) of the stator being carried away by the air so that all. undue heating of these parts is obviated and the electrical ei iciency of the machine is greatly increased.

I wish it to be understood that I do not by any means limit myself to the particular forms of conductors shown in the drawing and described in the specification, nor to the particular arrangement of a machine. as shown in the drawings, since my invention permits a great number of variations without departing from its principle or sacrificing any of its advantages.

Although the conductors shown in the drawings are metal bars or metal tubes in one piece, I may as well employ conductors madeup of a plurality of parts, such as stranded conductors or cables showing a longitudinal channel. Further, instead of air as a cooling agcnt, I may as well employ water or any other suitable gaseous or liqud medium, devices for cooling the rotating parts of electric machinery provided with hollow conductors by aid of water, being well known to those skilled in the art, so that it will be easy to apply these devices to the new combination according to the present invention.

-I claim:

1. In a high voltage dynamo in combination, a stator, slots`extending across the inner periphery of the said staton insulating tubes within said slots and hollow conductors within said tubes, said conductors adapted to have generated theni alternating Currents of a frequency producmg appreciable skin efl'ect, the hoilow tube portons permitting the ventilation of said conductors and means for directng a cooling medium through said hollow conductor por tions.

2., In a high voltage dynano in combination, a statoi', Slots extending across the periphery of said stator, insulating tuhes within said Slots, conductors of conpamtively great cross-sectional area within seid insuletng tubes, said conductors adapted to have enerated in them alternating Currents of a requency producing eppreciahie skin effect, said conuctors being provided With longitudinal Channels, to pernit ventilation of said conductors, and. means for irecting a cooling medium through said Channels.

3. In a high voltage dynano, in combinetion, a stator,s1ots extending across the inner periphery of said stator, insuiating tubes within said Slots, holiow conductors within said insulatng tubes, the walis of Saiti conductors and insulating tubes and the stator having corresponding opening-S in their middle parts.

4:. In e high Voltage dynamo, in combinetion a stator, Slots extending across the inne' periphery of said stator insulating tubes within said Slots, hollow conducto's within said insulating tubes, the Walls of said conductors and insulating tubes and the stztor having corresponding openings in their middle parts, and means for causing a cooling medium to pass into the open end of said conductor and through the said openings in the walls of said conductors and insulatin -tubes and in the stator.

In Wtness whereof I have hereunto set my signature in the presence of two subscribing witnesses.

REINHOLD RUDENBERG. witnesses:

WOIDEMAR HAUPT, Hmm! Hmmm. 

